THE PREPARATION OF CULTURE MEDIA 137 



achite green inhibits the growth of the colon bacillus without exerting 

 any such influence upon the typhoid bacillus. To make one liter: 



1. Prepare a neutral, one-half strength, meat-infusion bouillon 

 (500 grams of meat to 2 liters of water) by the usual technique. 



2. Acidify this with 7.5 c.c. of normal hydrochloric acid (to facilitate 

 the solution of agar). 



3. Dissolve in this 30 grams of agar (three per cent) by boiling. 



4. Neutrahze with 7 c.c. normal KOH or NaOH (until neutral to 

 litmus). 



5. Add 5 c.c. of normal sodium carbonate solution to make it alka- 

 line and heat in Arnold sterilizer for several hours. 



6. Add 100 c.c. of a ten per cent nutrose solution (one per cent). 

 This agar may be sterilized and stored in quantities of 100 c.c. without 

 further manipulation. 



7. Before use, redissolve, and to 100 c.c. add 2 to 2.9 c.c. of a two 

 per cent solution of malachite green (trade mark, "Hochst 120"). 

 This solution is made in sterilized water, but is not boiled. 



8. Fifteen to twenty c.c. of this medium are poured into Petri 

 dishes, allowed to cool, and inoculated by surface smears. 



Malachite-Green Bouillon (Peabody and Pratt).' — To 100 c.c. of 

 beef infusion broth add 10 c.c. of one per cent solution of malachite 

 green, Hochst 120, made with sterile water. This is tubed, 10 to 15 

 c.c. being put in each tube. 



This medium is used merely as an enriching fluid. One drop of the 

 suspected material (emulsified stool) is added to each tube and after 

 incubation for eighteen to twenty-four hours inoculations may be made 

 upon Conradi-Drigalski plates or other media. 



Peabody and Pratt found a reaction of .5 per cent acidity to phenol- 

 phthalein most favorable. 



Bile Medium.'^ — (Recommended for blood cultures by Buxton and 

 Coleman.) The mediiun is prepared as follows: 



Ox-bile 900 c.c. 



Glycerin 100 c.c. 



Pepton 20 grams 



Put into small flasks containing quantities of about 100 c.c. each and 

 sterilized by fractional sterilization. 



^ Peabody and Prcdt, Boston Med. and Surg. Jour., civiii, 7, 1908. 

 2 Conradi, Deut. med. Woch., 32, 1906. 



